This is a multi-center, open-label, single arm pivotal Phase III safety and clinical efficacy study in which patients will receive one course (four doses) of IDEC-102. Patients with follicular lymphoma will receive their first IDEC-102 treatment (Study Day 1) as soon as possible after confirmation by phone of their eligibility for study enrollment. There will be 100 evaluable patients entered on this multi-center study; approximately 10 of these patients will be entered at the University of Pittsburgh Cancer Institute.